Gísli Magnússon began his musical education at the age of 6 and attended piano lessons from the age of 8. From 2010-2013, he studied composition at the Iceland Academy of the Arts, first with Gunnar Andreas Kristinsson and later with Hróðmar Ingi Sigurbjörnsson and Atli Ingólfsson. In 2016 he finished his Master's studies at Conservatorium van Amsterdam where his main teachers were Joël Bons, Willem Jeths and Wim Henderickx.

In his music, Gísli frequently seeks inspiration in the nature of his home country, Iceland, and often paints clear and direct pictures of natural phenomena in tones. His works have been described with the following words:

“He creates soundscapes and has a great interest in the specific colors of the various instruments. There are also great contrasts between baldness and musical bustle. I experience his piece as a journey through a landscape.” – Arnold Marinissen

Gísli’s compostions have been performed by various musicians and ensembles such as Duo Harpverk, Söngsveitin Fílharmónía, members of Ensemble neoN, Score Collective, Elja Ensemble, Sjøforsvarets musikkorps and orchestras such as the CvA orchestra, conducted by Ed Spanjaard, and the Iceland Symphony Orchestra, conducted by Daníel Bjanason.